Hydraulic jack arrangement for casing operations in mining

ABSTRACT

This invention relates to a hydraulic jack arrangement, in particular for the mechanization of casing operations in mining, wherein the jack is provided with a stroke-measuring device consisting of pneumatic means driven by the jack piston and determining the issue of pneumatic signals in dependence on the position of the jack piston, for example signals conforming to a binary code which can be utilized to control operation of the jack arrangement in accordance with the mining plan.

United States Patent Inventor Hans Rieschel Essen, Germany App]. No. 752,563 Filed Aug. 14, 1968 Patented June 8, I971 Assignee Bergwerksverband G.m.b.II. Essen, Germany Priority Sept. 15, 1967 Germany P 15 83 068.9

HYDRAULIC JACK ARRANGEMENT FOR CASING OPERATIONS IN MINING I Claim, 2 Drawing Figs.

us. Cl 92 5, 92/31. I 37/625.l8

Int. CI FOII) 25/26 Field of Search 92/31, 33,

[56] References Cited UNITED STATES PATENTS 2,930,362 3/1960 Riester et a1 92/33 X 2,955,574 10/1960 Geyer 92/33 2,964,061 12/1960 Rawson et al... 137/625.18 X 3,003,470 10/1961 Geyer 92/33 X 3,092,082 6/1963 Geyer 92/33 X 3,417,663 12/1968 Beck et a1. 137/625.18 3,494,175 2/1970 Cusick et al. 137/625.18

Primary Examiner-Martin P. Schwadron Assistant Examiner-Leslie J. Payne AttorneyMalcolm W. Fraser ABSTRACT: This invention relates to a hydraulic jack arrangement, in particular for the mechanization of casing operations in mining, wherein the jack is provided with a stroke-measuring device consisting of pneumatic means driven by the jack piston and determining the issue of pneumatic signals in dependence on the position of the jack piston, for exam'ple signals conforming to a binary code which can be utilized to control operation of the jack arrangement in accordance with the mining plan.

PATENIED JUN 8 is?! FIG-.1

INVENTOR 292w FIELD OF THE INVENTION 1. Background .lack arrangements of the above kind are used in this context either directly as hydraulic pit props, steppingjacks, aligning jacks or sensing jacks, or are indirectly employed to influence the mechanization of the casing operation, via the advance on the face and possibly through the agency of the available working section, being used for example as stepping jacks for the conveyor system, as lifting jacks for same, or for that matter as servo actuators for adjusting the blades of the cutter.

2. Prior Art It is already known to produce a certain degree ol'extension travel in ajack arrangement, using a potentiometer to control solenoid valves associated with the casing operation. The potentiometer determines the design of the overall system employed to control the casing of the working, i.e. determines it as being an electrohydraulic system. Systems of this kind, because of the safety requirements which mining operations impose, are not always satisfactory. Also, the incorporation of a potentiometer in ajack arrangement gives rise to difficulties in practice.

It is also known to determine the end position of the jack arrangement, and therefore the full piston travel, for example by means of extractable cables (German Specification No. 1,182,184). Then, although it is possible to employ an arbitrary kind of system for controlling the operation of easing the working, the cables are a nuisance and are frequently insuffciently accurate for the purpose.

Finally, it has been proposed to indicate the terminal position of the piston in a jack arrangement of the kind in question, by a pneumatic-hydraulic control device (German Pat. application No. 6.6637), which can be introduced into a system which has recently been found to be particularly well suited for the mechanization of mine casing operations.

lt is a feature of the known proposals that they are limited to the determination of a piston stroke, generally speaking the maximum piston stroke. However, the information requirements of modern control systems intended for full automation of the operation of easing mine workings, make it necessary to be able to extend or retract the piston of a jack system by a specific extent, which can be suited in each particular situation, and/or to be able to determine such an extent at a control center and/or to be able to program it in a control system implementing the mining plan. 7

It is the object of the invention to create a hydraulic jack arrangement, in particular for the purpose of mechanizing casing operations in mining, which satisfies these preconditions. BRIEF SUMMARY OF THE INVENTION The realization of this object is achieved by a pneumatic stroke-measuring device built into the cylinder of the jack, said device employing a scale pierced by a plurality of spaced holes, which scale is movable by the piston of the jack past and between several opposed pairs of supply and exit passages for compressed gas in order to produce pneumatic signals corresponding to the particular piston positions.

Through the agency of the pairs of supply and exit passages, the stroke of the piston of the jack arrangement can be split into an arbitrary number of individual travels. However, a signal only appears at a specific pair of supply and exit passages if there is positioned between the particular pair of passages one of the holes in the positively operated scale.

The signals thus indicative of a specific position on the part of the piston can be picked up and displayed at a remote control center. Equally, however, they can be introduced as items ofinformation into a superordinate, pneumatic-hydraulic control system. Then, it is possible, by means of the quantity of hydraulic fluid fed to the jack arrangement, to dictate specific partial travels on the part of the piston. This is possible independently of any manufacturing tolerances and leakage losses, factors which, in the hydraulic jack "systems used in mine casing operations, are relatively important. Specific partial travels can also be successively dictated in program-controlled fashion in the context of a control system which carries out the planned course of the mining operation.

FURTHER FEATURES OF THE INVENTION Where the practical design of this kind ofjack arrangement, with a pneumatic stroke-measuring device and intended for mechanization applications (in particular in mining), is concerned, the problem then arising, namely of protecting the stroke-measuring device against external mechanical influences which could damage it or even destroy it, is simpiy solved by building the device into the jack cylinder. This is most simply achieved if, for this purpose, the stroke-measuring device is designed not as a linear or rule-type scale, but is so designed that it takes the form ofa rotatable perforated disc enclosed in a space formed within the cylinder at the base thereof, said cylinder also containing the supply and pickup passages in communication with said space. This space and these passages can be formed quite straightforwardly in the base of the cylinder and the device thus protected against all mechanical influences.

The rotatable perforated disc can accommodate a very large number of pieces of information. The design of the stroke-measuring device is made particularly simple when using a perforated disc of this kind if said disc is attached to a rigid spindle, that of whose ends projecting out of the disc space is positively operated by the piston of the jack and is subjected to the pressure of the hydraulic fluid. The differential between the pressure in the space containing the perforated disc and the pressure in the jack cylinder keeps the rigid spindle in position in a very simple bearing, such as a thrust bearing. This in turn enables a correspondingly compact arrangement of the stroke-measuring device, something which is frequently a prerequisite for the protective accommodation of the device in the cylinder of the jack.

The positive drive arrangement should be of the simplest possible design. This can be achieved using a spindle to drive the pneumatic scale and a nut fixed to the piston and screwing up and down said spindle.

Independently of the design of the positive drive, the incorporation of a step-up or stepdown transmission system into the drive may be advisable. In the individual case, this will depend upon the pitch of the spindle thread, upon the disc area or scale area available for accommodation of items of information, or also upon the number of items of information required.

DESCRIPTION OF PREFERRED EMBODIMENT The invention will now be further explained having regard to an example, described with reference to the accompanying drawings, in which:

FIG. 1 illustrates in longitudinal section'ajack arrangement in accordance with the invention; and

FIG. 2 is a section through the jack housing,- in which a stroke-measuring device for the jack is accommodated.

It will be assumed that the jack arrangement shown in FIG. I is a hydraulic pit prop for use in mining operations. The lower or outer part I of the pitprop accommodates a longitudinally extensible upper or inner part 2. the latter being held against rotation relative to the former.

The inner part 2 is provided at its lower end within the outer part 1 with a piston 13 which is sealed around its periphery at 14 relative to the internal wall of the outer part I. A spring 15 urges the piston towards the base of the outer part.

Between the base of the outer part I and that face of the piston 13 which faces it, a chamber is formed into which hydraulic fluid can be introduced, or from which it can be removed, through a passage 16, the arrow a indicates.

The pit prop is provided with a pneumatic stroke-measuring device. This consists of a scale driven positively, i.e. substantially without any slip, by the pit prop piston 13, the scale in this particular example taking the form of a disc 17. The disc 17 is carried adjacent the lower end of a spindle 18, which is carried in a ball thrust bearing 5. The disc 17 and lower end of the spindle 18 are accommodated with small clearance in a space defined by two matching recesses, one of which is formed in the base 19 of the outer pit prop part 1 and the other in a cylinder cover 20 whose external dimensions correspond to the dimensions of the base of the outer pit prop part.

The spindle 18 has an upper threaded section 3, which projects into a closed bore 21 extending through the piston 13 and part of the inner pit prop part 2. The piston 13 has a nut 4 attached to it and this, together with the threaded section 3 of the spindle, constitutes a positive drive arrangement for converting a particular piston position into a specific rotational position of the disc 17.

When under operating pressure, hydraulic fluid can flow through the clearance between the threads on spindle and nut into the space 2!. Thus, the full hydraulic pressure prevails at the end of the lower spindle l8. Consequently, the spindle 18 is forced up against the thrust bearing 5. A seal 6 prevents any hydraulic fluid escaping along the spindle 18.

The rotatable disc 17, enclosed in the space 7 inside the said housing, contains small holes. By means of these holes 12, pairs of passages 8, 9; 10, 11 etc., formed in the base of the outer part 1 and in the cover 20, of which passages the lower ones 9 and 11 are supply passages for compressed air and the upper ones 8 and are exit passages, can communicate with one another.

A continuous flow of compressed air exits from the passages 9, ll etc. lfa hole 12, as in FIG. 2, is in line with the passages 8 and 9, then a substantial laminar flow is created, by which energy is transferred and thus a circuit arranged in a superordinate control system actuated, or otherwise.

However, ifthe hole 12 is not located between the passages 8 and 9 but instead an intervening piece of the disc is disposed therebetween, then a turbulent state is created and no signal can be developed in the exitjet 8.

It is clear from this in dependence on the particular piston positions, binary signals are generated. These signals can be processed in the most varied ways in a control system. For example, it is possible to employ the signals to indicate the piston position. Equally, it is possible correspondingly to control the pit prop pressure so that the pit prop extends or retracts by a specific amount. This extension or retraction can be in accordance with a predetermined plan.

Since, moreover, it is binary signals which are involved, a great many piston positions can be reproduced so that the piston positions can be indicated virtually continuously.

The device required for this purpose is protected inside the pit prop orjack itself and is thus shielded against any external effects.

I. A stroke measuring device for hydraulic jacks for mining equipment for determining the issue of pneumatic signals responsive to the position of the jack piston, said device consisting of a hydraulic jack arrangement comprising:

an outer part constituting a cylinder;

an inner part constituting a piston movable within the cylinder and defining within the latter a chamber which can be supplied with hydraulic fluid under pressure;

means forming a space within the jack cylinder sealed from said hydraulic fluid chamber and having opposed openings arranged in pairs and constituting the termini of passages respectively;

a movable element in said space driven by the jack piston, said element having a plurality of orifices therein movable past and between the opposed openings into said space of each of a plurality of pairs of passages formed in the jack 0 linder; I an means for supplying pressurized pneumatic fluid to one of each pair of said passages, whereby pneumatic signals are issued from the others of said passages in dependence on the position of the jack piston, said movable element, passages and pneumatic supply means thus constituting a stroke-measuring device incorporated within the jack cylinder. 

1. A stroke measuring device for hydraulic jacks for mining equipment for determining the issue of pneumatic signals responsive to the position of the jack piston, said device consisting of a hydraulic jack arrangement comprising: an outer part constituting a cylinder; an inner part constituting a piston movable within the cylinder and defining within the latter a chamber which can be supplied with hydraulic fluid under pressure; means forming a space within the jack cylinder sealed from said hydraulic fluid chamber and having opposed openings arranged in pairs and constituting the termini of passages respectively; a movable element in said space driven by the jack piston, said element having a plurality of orifices therein movable past and between the opposed openings into said space of each of a plurality of pairs of passages formed in the jack cylinder; and means for supplying pressurized pneumatic fluid to one of each pair of said passages, whereby pneumatic signals are issued from the others of said passages in dependence on the position of the jack piston, said movable element, passages and pneumatic supply means thus constituting a stroke-measuring device incorporated within the jack cylinder. 